Palaeos:
AMNIOTA
THE VERTEBRATES
Amniota
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Amniota
Contents
Abbreviated Dendrogram
REPTILIOMORPHA
|
`--AMNIOTA
|--Casineria
|--Westlothiana
`--Crown Amniota
|--Sauropsida (= Reptilia)
| |--ANAPSIDA
| `--EUREPTILIA
`--SYNAPSIDA
Overview
Stem Amniota
Crown Amniota
Reptiles
Sauropsida
Dendrogram
References
The amniote egg was one of evolution's great success stories, because it allowed land animals to reproduce separately
from water. We don't really know when the transition from amphibian (dependemnt on water) to reptile (totally
terrestrial) occurred, but it was sometime during the early Carboniferous period, not long after the evolutionary
radiation of the amphibians (tetrapods). Indeed, it seems like proto-reptiles were among the first of these many
lineages to diverge, and a number of lineages, of various stages of advancement, co-existed with traditional
amphibians for many millions of years. It was only when the climate became drier and the great swamps dissappeared
that the reptiles had an advantage over their amphibious brethren. Here we continue the story of these proto-reptiles,
and speculate on when they made the transition from reptile-like amphian to amphibian-like proto-reptile.
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AMNIOTA
THE VERTEBRATES
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Crown Amniota
Contents
Abbreviated Dendrogram
REPTILIOMORPHA
|
`--AMNIOTA
|--Casineria
|--Westlothiana
`--Crown Amniota
|--Sauropsida (= Reptilia)
| |--ANAPSIDA
| `--EUREPTILIA
`--SYNAPSIDA
Overview
Stem Amniota
Crown Amniota
The Amniotes
Discussion of Phylogenetic Relationships
Temporal Fenestration and the Classification of
Amniotes
Description
Reptiles
Sauropsida
Dendrogram
References
Taxa on This Page
1. Amniota
Note: the present page is concerned with the Crown Group Amniotes, that is, the most recent common ancestor of all
living amniotes and all their descendants. It is very likely however that there were reptiles, that is, amniotes, existing
before then, and even that some of these are already known from the fossil record. The problem is, it is very difficult
to know exactly where amongst the various transitional forms between the amphian and reptilian condition reviewed
in the previous pages the ability lay eggs on dry land first appeared. But the distinction on this page is not the
physiological or evolutionary between pre-amniotes and amniotes, but the phylogenetic (family history of life)
distinction between the first amniotes (and associated non-amniotes) and one particular group of later (though still
very early and primitive) amniotes (reptiles) that became the ancestors of all later reptiles as well as mammals and
birds. MAK111121
The Amniotes:
Lungs: complex and in-folded, joined pharynx by trachea with cartilaginous
support. Lungs used for CO2 dumping as well as O2 intake due to keratinized
skin.
Neck: Often lengthened and more flexible.
Head: Buccal pumping eliminated, so head can be smaller and more domed.
Skull: (Captorhinid) Like "Anthracosaurs" but no otic notch or intertemporal. Postparietal, tabular and supratemporal
reduced and on occipital surface only. Supraoccipital supports posterior of braincase, large stapes supports it laterally.
Transverse flange on pterygoid. Elimination of large fangs. Basicranial articulation with palate moveable.
Basioccipital and exoccipital form occipital condyle. Fits in ring formed intercentra and arches of atlas: ball and
socket joint. Palatoquadrate reduced to quadrate and epipterygoid. Lower jaw has 1-2 coronoids and splenial.
Vertebrae: Spool-shaped centra. Small, crescentic intercentra.
Ventral axial muscles: Development of intercostals used to move ribs in respiration.
Ribs: lighter and may be joined ventrally by sternum as specialization for intercostal ventilation. Postural role
assumed by epaxial muscles which are no longer primary locomotor muscles.
Limb bones: lighter – possibly reflecting proprioreceptor system. Feet used as levers for propulsion, rather than
holdfasts. Ankle forms distinct hinge joint (mesotarsal). Tibiales, other bones of pes fuse to form astragalus. 23453
manus, 23454 pes.
Pelvis: Sacrum expanded from one vertebra to 2-3.
Hearing: convergent development of stapes (hyomandibula) as principal sound conduction mechanism of middle ear
(i.e. connects tympanum with inner ear).
Excretion: Duct linking kidney & cloaca. Bladder not used as much for water recovery. This function tends to be
performed by kidney.
Amniotic Egg: additional membranes (amnion, allantois chorion) in egg act to permit gas exchange but avoid water
loss, permit large amounts of yolk storage, isolate waste products during development.
Temporal Fenestra: Synapsid at squamosal-postorbital-jugal, diapsid add at parietal-squamosal-postorbital.
Euryapsid derived independently from diapsid by lack defined lower fenestra – loss of lower temporal bar. - ATW
Discussion of Phylogenetic Relationships
Michel Laurin and Jacques A. Gauthier
(Tree of Life project - Creative Commons Attribution)
Generations of systematists have studied amniote phylogeny at diverse genealogical levels, and until a few years ago,
its broad outlines were thought to be reasonably well understood. Indeed, recognition of the major living clades, such
as mammals, turtles and birds, antedates the Theory of Descent. Relations among these taxa, and especially the
connections of various fossils to them, have been contentious in post-Darwinian times. Much of that controversy can,
however, be attributed to the fact that during the first two-thirds of this century, there was little thought given to what
constituted evidence for phylogenetic relationships. The origins of the major extant lines of Amniota have become
clearer in the post-Hennigian era. Nevertheless, the precise relations of a number of clades, most notably the turtles
among extant forms and the aquatic and highly divergent ichthyosaurs and sauropterygians among extinct forms,
remain contentious.
Early phylogenetic analyses placed turtles outside of the remaining amniotes (only crown-clade names are listed to
simplify the trees):
Gauthier et al. (1988a, b, and c) later placed turtles as the sister clade to Sauria (crown-diapsids), and this topology
has now gained wide acceptance, at least among morphologists and paleontologists:
However, Rieppel (1994, 1995), Rieppel & deBraga (1996) and deBraga & Rieppel (1997) have suggested that turtles
may be the sister clade to lepidosaurs. This requires that turtles are saurians who have lost both the upper and lower
temporal fenestrae (holes in the skull associated with jaw muscles) so diagnostic of diapsid reptiles:
The three trees presented above include only extant taxa, and many phylogenetic analyses of amniotes have ignored
extinct taxa. However, it is important to bear in mind that discovering the globally most parsimonious tree requires the
inclusion of extinct taxa in a phylogenetic analysis (Gauthier et al., 1988b). Without fossils, the best-supported tree
for amniotes inferred from morphological data is the following (although only one more step is required to switch the
positions of lepidosaurs and turtles):
Recent molecular evidence for amniote relationships conflicts with paleontological and morphological evidence.
Initially, some gene sequences suggested a close relationship between birds and mammals, although never with strong
statistical support (e.g., Bishop & Friday, 1987; Goodman et al., 1987; Hedges et al., 1990). More recently, a study of
the molecular evidence for the origin of birds (15 genes; 5280 nucleotides, 1461 amino acids) discovered strong
support (100% bootstrap P value, BP) for a close relationship between birds and crocodilians (Hedges, 1994). A
smaller data set of 11 transfer RNA genes (686 sites) also resulted in a bird-crocodilian grouping (Kumazawa &
Nishida, 1995). A basal position for mammals was supported (99% BP) by analysis of a 3 kilobase portion of the
mitochondrial genome containing the two ribosomal RNA genes (Hedges, 1994). In the same study, a Sphenodonsquamate relationship also was found, but support for that grouping and for the position of turtles was not very strong.
The most recent molecular phylogenies have generally placed turtles among archosauromorphs, and often within
archosaurs (Mannen et al., 1997; Mannen & Li, 1999; Hedges & Poling, 1999; Hugall et al., 2007). The latter
placement is the least compatible with the morphological evidence, and no convincing explanation has been found so
far to explain this discrepancy.
At least two total evidence analyses (in which molecular and morphological data are combined) suggest that turtles are
not diapsids (Lee, 2001; Frost et al., 2006). In both, the molecular characters are much more numerous than the
morphological ones, which implies significant support for the placement of turtles outside diapsids in these molecular
datasets.
Many gene sequences of birds and mammals exist, but the relatively small number of sequences from representatives
of other amniote lineages, especially tuataras (Sphenodon) and turtles, has hindered the estimation of a robust
molecular phylogeny for all major groups of living amniotes. This is reflected by the low resolution of the molecular
phylogeny obtained by Hedges & Poling (1999) when Sphenodon (using only sequences of genes available in
Sphenodon) was included:
Without Sphenodon and using the greater number of sequences available for other taxa, Hedges & Poling obtained the
following fully resolved phylogeny, in which turtles are the sister-group of crocodilans:
Developmental data has rarely been used to study this question, but it has recently been found to place turtles outside
diapsids (Werneburg & Sánchez-Villagra, 2009).
If extinct amniotes are considered, the phylogeny is much more complex and controversial. Formerly, captorhinids
were believed to be closely related to turtles (Gauthier et al., 1988b, c), but more recently, several groups of
parareptiles have been sugested as closest relatives of turtles, such as procolophonids (Reisz & Laurin, 1991; Laurin
& Reisz, 1995), pareiasaurs (Lee, 1993, 1994, 1995, and 1996), and Eunotosaurus (Lyson et al., 2010). Some
paleontologists (Rieppel, 1994, 1995; Rieppel & deBraga, 1996; deBraga & Rieppel, 1997) place turtles among
diapsids, especially as the sister-group of euryapsids (a group of Mesozoic marine diapsids). Phylogeny and
Classification of Amniotes provides information about the phylogenies incorporating extinct amniote taxa, and
provides a detailed classification of the relevant groups. Temporal Fenestration and the Classification of Amniotes
discusses how temporal fenestration has been used to classify amniotes, and how tempororal fenestration evolved.
References
(Overworked editor's note: at some point these references need to be hyperlinked with the above, formatted (italics
etc) and transferred to the reference page MAK111106)
Bishop, M. J., & A. E. Friday. 1987. Tetrapod relationships: the molecular evidence. In Patterson, C (ed.) Molecules and Morphology in Evolution:
Conflict or Compromise?: 123-139. Cambridge: Cambridge University Press.
Campbell, N. A. 1993. Biology. 3rd edition. New York: The Benjamin/Cummings Publishing.
Carroll, R. L. 1964. The earliest reptiles. Zoological Journal of the Linnean Society 45: 61-83.
Coyne M. 1999. World's oldest reptile nest found. Marine Turtle Newsletter 83: 21.
deBraga M. & O. Rieppel. 1997. Reptile phylogeny and the interrelationships of turtles. Zoological Journal of the Linnean Society 120: 281-354.
Frost D. R., T. Grant, J. Faivovich, R. H. Bain, A. Haas, C. F. B. Haddad, R. O. de Sá, A. Channing, M. Wilkinson, S. C. Donnellan, C. J.
Raxworthy, J. A. Campbell, B. Blotto, P. Moler, R. C. Drewes, R. A. Nussbaum, J. D. Lynch, D. M. Green, & W. C. Wheeler. 2006. The
amphibian tree of life. Bulletin of the American Museum of Natural History 297: 1–370.
Gaffney, E. S. 1980. Phylogenetic relationships of the major groups of amniotes. In A. L. Panchen (ed.) The Terrestrial Environment and the
Origin of Land Vertebrates: 593-610. London: Academic Press.
Gauthier, J. A. 1994. The diversification of the amniotes. In D. R. Prothero and R. M. Schoch (ed.) Major Features of Vertebrate Evolution: 129159. Knoxville: The Paleontological Society.
Gauthier J., R. Estes, & K. de Queiroz. 1988a. A phylogenetic analysis of Lepidosauromorpha. In: R. Estes and G. Pregill (eds.) Phylogenetic
relationships of the lizard families: 15-98. Stanford: Stanford University Press.
Gauthier, J., A. G. Kluge, & T. Rowe. 1988b. Amniote phylogeny and the importance of fossils. Cladistics 4: 105-209.
Gauthier, J., A. G. Kluge, & T. Rowe. 1988c. The early evolution of the Amniota. In M. J. Benton (ed.) The phylogeny and classification of the
tetrapods, Volume 1: amphibians, reptiles, birds: 103-155. Oxford: Clarendon Press.
Goodman, M., M. Miyamoto, & J. Czelusniak. 1987. Pattern and process in vertebrate phylogeny revealed by coevolution of molecules and
morphologies. In C. Patterson (ed.) Molecules and Morphology in Evolution: Conflict or Compromise?: 141-176. Cambridge: Cambridge
University Press.
Hedges, S. B. 1994. Molecular evidence for the origin of birds. Proceedings of the National Academy of Sciences of the United States of America
91:2621-2624.
Hedges, S. B., K. D. Moberg, & L. R. Maxson. 1990. Tetrapod phylogeny inferred from 18S and 28S ribosomal RNA sequences and a review of
the evidence for amniote relationships. Molecular Biology and Evolution 7:607-633.
Hedges S. B. & L. L. Poling. 1999. A molecular phylogeny of reptiles. Science 283: 998-1001.
Hugall A. F., R. Foster, & M. S. Y. Lee. 2007. Calibration choice, rate smoothing, and the pattern of tetrapod diversification according to the long
nuclear gene RAG-1. Systematic Biology 56: 543–563.
Kumazawa, Y., & M. Nishida. 1995. Variations in mitochondrial tRNA gene organization of reptiles as phylogenetic markers. Molecular Biology
and Evolution 12:759-772.
Laurin, M. & R. R. Reisz. 1995. A reevaluation of early amniote phylogeny. Zoological Journal of the Linnean Society 113: 165-223.
Laurin M. & M. Girondot. 1999. Embryo retention in sarcopterygians, and the origin of the extra-embryonic membranes of the amniotic egg.
Annales des Sciences Naturelles, Zoologie, Paris, 13e SÈrie 20: 99-104.
Laurin M. & R. R. Reisz. 1999. A new study of Solenodonsaurus janenschi, and a reconsideration of amniote origins and stegocephalian evolution.
Canadian Journal of Earth Sciences 36: 1239-1255.
Laurin M., R. R. Reisz, & M. Girondot. 2000. Caecilian viviparity and amniote origins: a reply to Wilkinson and Nussbaum. Journal of Natural
History 34: 311-315.
Lee, M., S. Y. 1993. The origin of the turtle body plan: bridging a famous morphological gap. Science 261: 1716-1720.
Lee, M. The turtle's long-lost relatives. Natural History, April 1994, 63-65.
Lee, M. S. Y. 1995. Historical burden in systematics and the interrelationships of 'Parareptiles'. Biological Reviews of the Cambridge Philosophical
Society 70: 459-547.
Lee M. S. Y. 1996. Correlated progression and the origin of turtles. Nature 379: 812-815.
Lee M. S. Y. 2001. Molecules, morphology, and the monophyly of diapsid reptiles. Contributions to Zoology 70: 1-18.
Li C., X.-C. Wu, O. Rieppel, L.-T. Wang, & L.-J. Zhao. 2008. An ancestral turtle from the Late Triassic of southwestern China. Nature 456: 497–
501.
Lombardi J. 1994. Embryo retention and evolution of the amniote condition. Journal of Morphology 220: 368.
Lyson T. R., G. S. Bever, B.-A. S. Bhullar, W. G. Joyce, & J. A. Gauthier. 2010. Transitional fossils and the origin of turtles. Biology Letters 6:
830–833.
Mannen H., S. C.-M. Tsoi, J. S. Krushkal, W.-H. Li, & S. S.-L. Li. 1997. The cDNA cloning and molecular evolution of reptile and pigeon lactate
dehydrogenase isozymes. Molecular Biology and Evolution 14: 1081-1087.
Mannen H. & S. S.-L. Li. 1999. Molecular evidence for a clade of turtles. Molecular Phylogenetics and Evolution 13: 144-148.
Modesto S. P. 1999. Observations on the structure of the Early Permian reptile Stereosternum temidum Cope. Palaeontologia Africana 35: 7-19.
Reisz, R. R., & M. Laurin. 1991. Owenetta and the origin of turtles. Nature 349: 324-326.
Rieppel, O. 1994. Osteology of Simosaurus gaillardoti and the relationships of stem-group sauropterygia. Fieldiana Geology 1462: 1-85.
Rieppel O. 1995. Studies on skeleton formation in reptiles: implications for turtle relationships. Zoology-Analysis of Complex Systems 98: 298308.
Rieppel O. & M. deBraga. 1996. Turtles as diapsid reptiles. Nature 384: 453-455.
Rieppel O. & R. R. Reisz. 1999. The origin and early evolution of turtles. Annual Review of Ecology and Systematics 30: 1-22.
Smithson T. R. 1989. The earliest known reptile. Nature 342: 676-678.
Smithson T. R., R. L. Carroll, A. L. Panchen, & S. M. Andrews. 1994. Westlothiana lizziae from the VisÈan of East Kirkton, West Lothian,
Scotland, and the amniote stem. Transactions of the Royal Society of Edinburgh 84: 383-412.
Stewart J. R. 1997. Morphology and evolution of the egg of oviparous amniotes. In: S. Sumida and K. Martin (ed.) Amniote Origins-Completing
the Transition to Land (1): 291-326. London: Academic Press.
Werneburg I. & M. R. Sánchez-Villagra. 2009. Timing of organogenesis support basal position of turtles in the amniote tree of life. BMC
Evolutionary Biology 9: 9 pages.
Temporal Fenestration and the Classification of Amniotes
(Tree of Life project - Creative Commons Attribution)
Temporal fenestration has long been used to classify amniotes (Osborn, 1903). Taxa such as Anapsida, Diapsida,
Euryapsida, and Synapsida were named after their type of temporal fenestration. Temporal fenestra are large holes in
the side of the skull. The function of these holes has long been debated (Case, 1924), but no consensus has been
reached. Many believe that they allow muscles to expand and to lengthen. The resulting greater bulk of muscles
results in a stronger jaw musculature, and the longer muscle fibers allow an increase in the gape (Pirlot, 1969).
An important distinction must be made between the type of fenestration found in certain taxa, and the taxa that were
named after these types of fenestration. For instance, the anapsid condition is characterized by the lack of temporal
fenestrae (Figure 1). As such, it is primitive for amniotes because all their close relatives lack temporal fenestrae.
Anapsida (the taxon) includes turtles and their extinct relatives. While most members of this taxon (but not
lanthanosuchids and some millerettids) have an anapsid skull, some extinct relatives of saurians (such as captorhinids
and "protorothyridids") also had anapsid skulls.
Four main patterns of temporal fenestrae in amniote skulls a) anapsids, b) synapsids, c)
diapsids), d) euryapsids. (j. jugal, p. parietal, p.o. postorbital, sq. squamosal) (Benton, 2005).
original url
The synapsid condition is characterized by the presence of a single temporal fenestra bordered minimally by the jugal,
postorbital, and squamosal. The quadratojugal and the parietal occasionally contribute to the edge of this fenestra. By
comparison with diapsids, this fenestra can be called a lower temporal fenestra. All early members of Synapsida, the
taxon that includes mammals and their extinct relatives, had a synapsid skull, but the temporal fenestra has been
drastically modified in mammals by ventral processes of the frontal and the parietal that occlude the temporal fenestra.
The location of the old fenestra is still visible between the zygomatic arch, the orbit, and the dorsal part of the skull,
but it is no longer a hole in the skull. A few taxa not related to Synapsida have also acquired a lower temporal
fenestra. These include lanthanosuchids (Ivakhnenko, 1980) and some millerettids (members of Anapsida).
The diapsid condition is characterized by the presence of two temporal fenestrae, called the lower and the upper
temporal fenestrae. The lower temporal fenestra is similar to the fenestra of synapsids, and it is generally bordered by
the same bones (the jugal, postorbital, squamosal, and occasionally, the quadratojugal). The upper temporal fenestra is
bordered by the postorbital, squamosal, parietal, and often, the postfrontal. This type of fenestration apparently
appeared only once, in Diapsida, but it has been altered in many members of this taxon (squamates, and some early
archosauromorphs, for example) by the loss of the lower temporal bar formed by the jugal and the quadratojugal.
The last type of fenestration called euryapsid has been the most problematic, partly because the origin of this
condition has long been debated. It now appears that this condition is modified from the diapsid condition, and that it
appeared more than once. Euryapsid skulls have only an upper temporal fenestra, usually bordered by the parietal,
postfrontal, postorbital, and squamosal. Examples of euryapsid skulls include Araeoscelis, a Lower Permian
araeoscelidian, placodonts, nothosaurs, and plesiosaurs (marine reptiles of the Mesozoic). Euryapsida is a taxon that
includes most known euryapsids, except for Araeoscelis (Rieppel, 1993). The condition found in ichthyosaurs is
sometimes distinguished from the euryapsid condition because their temporal fenestra is only bordered by the parietal,
postfrontal, and supratemporal (Pirlot, 1969). This condition has been called parapsid, but it only represents a minor
variation on the euryapsid pattern.
References
Carroll R. L. 1981. Plesiosaur ancestors from the Upper Permian of Madagascar. Philosophical Transactions of the Royal Society 293: 315-383.
Case E. C. 1924. A possible explanation of fenestration in the primitive reptilian skull, with notes on the temporal region of the genus Dimetrodon.
Contributions from the Museum of Geology, University of Michigan 2: 1-12.
Heaton M. J. 1979. Cranial anatomy of primitive captorhinid reptiles from the Late Pennsylvanian and Early Permian Oklahoma and Texas.
Bulletin of the Oklahoma Geological Survey 127: 1-84.
Ivakhnenko M. F. 1980. Lanthanosuchids from the Permian of the East European platform. Paleontological Journal 1980: 80-90.
Laurin M. & R. R. Reisz. 1995. A reevaluation of early amniote phylogeny. Zoological Journal of the Linnean Society 113: 165-223.
Osborn H. F. 1903. On the primary divison of the Reptilia into two sub- classes, Synapsida and Diapsida. Science 17: 275-276.
Pirlot P. 1969. Morphologie évolutive des chordés. Montréal: Les Presses de l'Université de Montréal.
Reisz R. R. 1981. A diapsid reptile from the Pennsylvanian of Kansas. University of Kansas Publications of the Museum of Natural History 7: 174.
Rieppel O. 1993. Euryapsid relationships: A preliminary analysis. Neuen Jahrbuch für Geologie und Paläontologie. Abhandlungen 188: 241- 264.
Descriptions
Amniota:
Range: from the Late Carboniferous.
Phylogeny: Cotylosauria : Diadectomorpha + Stem
Amniota : ?Casineria + ? Westlothiana * : Synapsida +
Sauropsida.
Characters: premaxilla with palatal, maxillary & nasal
processes [MR05]; frontal contacts orbit; various patterns
of fenestration related to additional musculature for jaw
from dermal skull and development of musculature to
supply static pressure at jaw; squamosal contributes to
margin of posttemporal fenestra; hemispherical &
ossified occipital condyle; pterygoid with distinct palatal
surface, transverse flange and quadrate ramus [MR05];
pterygoid quadrate ramus with separate dorsal flange
extending from basicranial articulation to dorsal process of quadrate, supporting elongate epipterygoid [MR05]; loss
of labyrinthodont teeth, caniniform tooth present on maxilla; 2 centers of ossification in scapulocoracoid; astragalus
present. Numerous additional characters listed above.
Links: Introduction to the Amniota; Amniota; Amniota.
References: Müller & Reisz (2005) [MR05]. ATW051015.
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Stem Amniota
Casineria and Westlothiana
Contents
Abbreviated Dendrogram
REPTILIOMORPHA
|
`--AMNIOTA
|--Casineria
|--Westlothiana
`--Crown Amniota
|--Sauropsida (= Reptilia)
| |--ANAPSIDA
| `--EUREPTILIA
`--SYNAPSIDA
Overview
Stem Amniota
Crown Amniota
Reptiles
Sauropsida
Dendrogram
References
Taxa on This Page
1. Amniota
2. Casineria X
3. Westlothiana X
The first reptile
A some point in evolutionary history, at a time when the first great coal swamps were only just emerging, and before
even insects had taken wing, a tiny reptile-like amphibian aquired the ability to lay small waterproof eggs on land.
This great grand mother of all reptiles, birds, and mammals (including us) probably wasn't more than 10 cm (or 4
inches in old imperial measurement), in length, and for all the world resembled a small salamander or lizard. It would
have lived amongst leaf litter, rotten logs, and other hideaways, where it was safe from predators, and could scrurry
after and munch happily on the numerous arthropods that even then inhabited the Earth. We don't know the
transitiobnal stages that enabled it to liberate its reproductive cycle from water, culminating in the ability to lay
waterproof eggs that hatched into miniature adult-like young, bypassing the amphibian tadpole stage altogether. We
can be pretty sure that this creature was prior by some millions of years to the most recent common ancestor of all
living reptiles birds and mammals, but we don't know exactly by how much, or how physiologically primitive or
advanced it was. It may have resembled one of the two creatures featured on this page, or primitive(Solenodonsaurus
featured on a previous page. Or it may have different to all of them. We do know that that that tiny creatuere was the
beginning of one of the most successful animal clades to inhabit the Earth, the amniotes. MAK111109
Descriptions
Amniota: The first physiological reptiles, and all their descendents
Range: from the Early Carboniferous.
Phylogeny: Cotylosauria : Diadectomorpha + * : Casineria + Westlothiana + Crown Amniota
Comment: This taxon is erected here as a hypothetical apomorphy based node, defined by the presence of the first
amniote egg. This stem-based taxon is prior to, and hence more inclusive than, the crown-based taxon (crown
amniotes) referred to later. We don't know when this appeared, so the position of this clade is purely sp[eculative, as
are the relations to it of the other taxa on this and related pages, which may or may not have been actual amniotes.
MAK111121.
Casineria: C. kiddi Paton, Smithson & Clack 1999
Range: Early Carboniferous (Asbian - Middle Visean) of
Scotland. (Cheese Bay Shrimp Bed of the East Lothian Lower
Oil Shale)
Phylogeny: Stem Amniota : Westlothiana + Crown Amniota +
*
Comments: Poorly known form, known only from a headless
partial skeleton, but with several tantalising early aamniote
features, such as unfused ankles and clawed toes, five fingers,
and gracile build with light leg-bones. Of course these may
simply be convergences due to common adaption of a shared
environment, or it may be that Casineria is indeed the earliest
known reptile. In any case, this is the earliest known fully
terrestrial tetrapod. The single tiny specimen shows bones that
are strongly ossified (not cartiligeinous) indicating that the
animal was almost or completely grown when it died. This ties
in with the hypothesis proposed by Carroll that the first
amniotes would have been very small, mo more than 10 cm,
due to the initial lack of extra-embryonic membranes that are
unique to amniotes (amnion, chorion, and allantois) and hence
problems with build up of carbon dioxide (Carroll 1970, 1991,
Laurin 2004 p.594). Initial cladistic analysis (Paton et al 1999)
suggested a polytomy with Westlothiana and Eureptilia
(Captorhinus, Paleothyris, Petralocosaurus), but the
consensus tree was highly instable. Supertree analysis by Ruta
et al 2003b place it close to Westlothiana, another enigmatic form, which may or may not be an amniote, and place
both species outside a surprising clade in which diadectomorphs are nested in a paraphyletic amniota. For now we
have tentatively and provisionally placed Casineria as a very primitive amniote. The generic name is is a latinization
of Cheese Bay, the site near Edinburgh, where the specimen was found (not a native Australasian evergreen).
Links: Out of the Swamps - How early vertebrates established a foothold with all 10 toes on land - Richard
Monastersky .; Wikipedia; Jenny Clack - Other Early Tetrapod Projects (Casineria gets a brief mention)
Image: Casineria kiddi holotype from Wikipedia; skeleton reconstruction and silhouette David Peters - Reptile
evolution
References: Paton et al 1999 MAK111106
Westlothiana:
W.
lizzaie Smithson &
Rolfe 1990
Range:
Early
Carboniferous
(Brigantian - Late
Visean) of Scotland.
(lower East Kirkton
Limestone,
West
Lothian Upper Oil
Shale
Formation,
Scotland)
Phylogeny: Stem Amniota : Casineria + Crown Amniota + *
Comments: named after the West Lothian district where it was discovered, and known from two nearly complete
skeletons. A transitional form that combines amphibian and reptilian features, it was originally cosidered a a eureptile
based on similarities of the skull, humerus, and vertebrae. Features that asociate it with amniotes rather than
amphibians include unfused ankle bones, lack of labyrinthodont infolding of the dentin, a lack of an otic notch and a
generally small skull. Later placed outside the amniote crown because of the absence of diagnosable characters, and
now considered to belong on the amniote stem, close to either diadectomorphs or lepospondyls [1]. However its
precise affinities remain uncertain, and the absense of crown group traits need not mean it is not an amniote, albeit a
stem group amniote. As with Casineria , and in keeping with Carroll's hypothesi of amniote origins, these were small,
terrestrial animals (total length 20 cm). The elongate body and small legs could be an adaption to burrowing, as with
skinks.
Image: Skeleton reconstruction and silhouette David Peters - Reptile evolution; life reconstruction Nobu Tamura
Wikipedia
References: Smithson & Rolfe 1990, van Tuinen & Hadly 2004, Wikipedia MAK111106
Note: [1] David Marjanovic, who at the time of writing is working on a very large cladistic analysis, argues is a basal
lepospondyl with ordinary lepospondyl tabulars (See Dinosaur Mailing List) MAK111109
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Amniota : Reptiles
Contents
Abbreviated Dendrogram
REPTILIOMORPHA
|
`--AMNIOTA
|--Casineria
|--Westlothiana
`--Crown Amniota
|--Sauropsida (= Reptilia)
| |--ANAPSIDA
| `--EUREPTILIA
`--SYNAPSIDA
Overview
Stem Amniota
Crown Amniota
Reptiles
Sauropsida
Dendrogram
References
Taxa on This Page
1. Reptilia
A meditation on Reptiles
Reptiles - those creeping, crawling, slithering, scaley, animals, dragons and dinosaurs, creatures of
myth and folklore. Who hasn't had their imagination stirred by these creatures and their chthonic,
typhonic, consciousness?
Yet in order to understand reptiles and their place in the evolutionary history of life on Earth, we
need to get rid of a few myths and misconceptions
A lot of what the common person knows or thinks about reptiles is determined by cultural prejudice.
The whole idea of the reptile, especially derived squamata, as the archetypal reptile, as a coldblooded, terrifying, evil and sinister creature, has its roots in teh Judae-Christian creation myth
(bottom left), although its hould be pointed out that there are also more subtle and psychologically
nuanced readings than the usual literalism. But it's just a small leap of unscientific imagination from
the serpent in the Garden to Extraterrestrial shapeshifter (below center). Thebiblical phobia of
creeping animals probably also ties in with the new paradigm meme of the reptilian brain as the
most archaic, atavaistic, and savage stratum of brain evolution (below right)
Negative, Western Judaeo-Christian inspired, images of reptiles:
Judaeo Christian serpent in the Garden of Eden
myth. according to a literalist religion , responsible,
like women women for all of man's problems.; image
from Serpent Mythology
New Age conspiracy theory, according to which
extraterrestrial reptilian aliens masquerade as public
figures like the two President Bushes and and the British
Royal Family ) as part of a dastardly alien plan for world
domination. Image from Reptilian Resistance movement
The the reptilian brain
as pertaining to coldblooded hierarchical
dominance. Image
from Alice in
Wonderland and the
World Trade Centre
Disaster by David Icke
Not surprisingly, all of these myths and prejudices are incorrect. Rather than being "cold blooded", reptiles are poikilotherms, in that their body temperature varies according to
environmental conditions or physiological activity (and in the tropics or even temeprate regions after being warmed by the sun or a period of activity they would be "warm blooded"),
in contrast to homeotherms such as some fish, dinosaurs, birds, and mammals which maintain thermal homeostasis (feedback and equilibrium. In premodern worldviews, worms and
snakes and other limbless crawling creatures are easily conflated, similar to the biblical confusion of birds and bats, The whole New Age reptilioid conspiracy theory (as well as ufo
reptilians in general) can be memetically derived from (as well as chronologically predated by) the miniseries and television series "V"; serpents. The triune brain hypothesis, with its
linear succession of reptilian old brain, paleomammalian limbic system, and neommalian neocortex, is no longer held to be a valid model of the evolution of the forebrain, classical
reptiles rather than being savage and instinctual often display complex behaviour, intelligence, and even care of the young, birds (which are essentially modified (dinosaurian)
"reptiles") have sophisticated neocortical learning fuctions, and some fish "limbic" style parental care [1]).
Interestingly, in other religions, such as Hinduism, Hermeticism, and some forms of Gnosticism, which are based more in contemplative spirituality and meditation rather than
authoritarian legalism, snakes have a much better reputation, being considered symbols of wisdom. We find this more positive association even in the current fantasy genre, where the
dragon generally has a high status.
Positive images of reptiles:
Marble relief of Asclepius and his daughter Hygieia, with
serpent. From Therme, Greece, end of the 5th century BC.
Istanbul Archaeological Museums. Asclepius was the ancient
Greek God of Medicine and Healing;. The rod of Asclepius, a
Cambodian statue of the Buddha, shielded by the Naga
(serpent being) Mucalinda (dated 1150 - 1175 c.e.); Asian
Drawing
by
Theodoros
Pelecanos,
in
alchemical
tract titled
Synosius
(1478),
depicting
Ouroboros,
the
snake-entwined staff, remains a symbol of medicine today,
although sometimes the caduceus, or staff with two snakes, is
used instead.
Photo by Prioryman, Wikipedia, GNU Free Documentation/Creative Commons
Attribution
Arts Museum in San Francisco.
Photo by DoktorMax, Wikipedia, public domain
serpent or
dragon
swallowing
its own
tail, a
symbol of
infinity.
Photo by
Carlos
adanero,
Wikipedia,
public
domain
As someone who loves reptiles (and other creatures) the present author cannot help but feel more attraction for these positive images, and a strong antipathy for the negative, religious
and conspiracy theory memes.
But of reptiles themselves? Freed of human anthropocentrism and psychological
projections both positive and negative, they are an assortment of animals living their
own lives and evolving in their own direction.
Their story is indeed a fascinating one, but whether reptiles even constitute a valid
taxon is now a disputed in biology. Originally they were given the rank of class in the
Linnaean system (although originally grouped by Linnaeus with the amphibians in his
Systema Naturae). The Linnaean system howeveris a static classification, not a
dynamic picture of the tree of the evolution of life on Earth. Our understanding of the
evolutionary history of reptiles and their era they ruled the Earth seems to have passed
through three broad stages.
In the 19th century, ancient saurians caught the popular imagination with the great
paleontological discoveries of the Victorian Age. Hence images of antediluvial
monsters, primordial creatures of ancient swamps. This soon settled down to more
serious science, although it was a while before dinosaurs were no longersprawling
overgrown lizards.
Four species of extant reptiles: Clockwise from above left: Spectacled Caiman (Caiman
crocodilus), Green Sea Turtle (Chelonia mydas), Tuatara (Sphenodon punctatus) and Eastern
Diamondback Rattlesnake (Crotalus adamanteus). Wikipedia
By the late nineteenth and early twentienth century, Darwin's revolution
had well and truly shaped scientific thinking, replacing early 19th century
Owenist archetypes and Cuverian sequential creationisms of the early 19th
century with a synthesis of Darwinian natural selection, Mendelian
inheritence, population genetics, and paleontology and a sense of evolution
through deep time. This is represented by the Evolutionary Systematics.
Here the books of Romer and, on a less technical level, Colbert, informed
a generation of budding paleo enthusiasts
The diagram at the left can be compared with the similar diagram
regarding the evolution of amphibians. Both have ancestral groups
(ichthyostedids, cotylosaurs, thecodonts) from which radiate a whole slew
of descendants; both have familiar and easily defined (in terms of recent
species) categories such as classes Amphibia and Reptilia.
Evolution of reptiles, graphic from Introductory Biology ECOL182R (Schaffer/Bonine/Ferriere) Spring 2009
Credited to Freeman 3rd edition Ch 27 (not sure what the book is called, but it is surprising to find this old
repeeresentation (with mid 20th century vintage drawings) in a current text book (the only concession to
current thinking is that Cotylosaurs are now referred to as "amphibians" (with a picture of Seymouria at the
bottom)
Among the advantages of evolutionary systematics is the emphasis on ancestral
groups and clear and easily identifiable categories (we all know what a reptile
is, or a bird or a mammal). The disadvantages are a lack of detail when it comes
to the order of branching of the phylogenetic tree of life (instead there is simply
a sort of star pattern radiating of many different groups from a general ancestor)
and that, whilst familiar representatives of a group are recognisable (we easily
associate a scaly crawling crocodile with "reptile", but what about a furry,
warm-blooded pterosaur). Because of this, the characteristics that define the
group as a whole can be generic or ambigious, and often both primitive
ancestral and highly specialised or derived types often cannot be so easily
identified. The phylogenetic-based cladistic system was an attempt to introduce
precision into this whole arrangement. It does this by rejecting all paraphyletic
groups. Here the old Class Reptilia becomes the paraphyletic taxon par
excellence. This is because reptiles are defined only by shared primitive
characteristics, essentially all amniotes that are not mammals or birds are
reptiles; a cladistically meaningless statement (whether it is phylogenetically
meaningless depends on your definition of phylogeny - evolutionary systamists
and cladists use the same word in very different ways!). Instead, reptilia is
replaced by a number of other nested clades, as shown in the diagram on the
right. Here, the green shaded area represents the Linnaean taxonomic category
"reptiles" (or Class Reptilia). This includes primitive synapsida - the
pelycosaurs and therapsids (shown by the shading over the bottom half of the
line leading to Synapsida; this is not technically the correct way to present a
cladogram (the diagonal here would have to be divided into further branching
points), but is still useful as a simple diagram) - but not advanced synapsids
A rather imprecise diagram ("fish" are not a terminal or monophyletic taxon!) showing the relationship
(mammals). It also inckudes turtles and tortoises (testudines), lizards and snakes between cladistic (diagonal lines) and traditional classification (shaded region) of the class Reptilia. The
and their relatives (lepidosaurs), and crocodiles and many extinct related types, traditional definition of Reptiles is a paraphyletic assemblage compromising all amniote lineages, with
but not birds (class Aves), despite their being closely related to crocs, as the the exception of birds and of mammalian synapsids. Vertebrata, Tetrapoda, Amniota, Sauropsida,
and so on represent a nested series of clades. Each "lower" clade (in the diagram) includes
diagrams. Obviously, the two systems are totally incompatible, which doesn't Diapsida,
the next two above it. Diagram by Petter B�ckman, Wikipedia
mean that one is wrong and the other right. Simply that they are two different
ways of making sense of the natural, biological world. Of these two systems, cladstics has been almost universally adopted by vertebrate paleontologists, because it provides a
standardised methodology for testing phylogenetic hypotheses (i.e. proposals about phylogeny, not the actual deep time historical fact of phylogenetic relationship). That doesn't mean
that evolutionary systematics is automatically wrong, just its a different methodology; all these methodologies are useful each in their own way.
For this reason, we retain use reptile here in both the colloquial, the Linnaean, and the evolutionary systematic, sense of four-legged or secondarily limbless, ectothermic (heat from
external environment) or poikilothermic (body temperature varies widely) animals (more properly vertebrates) (apart from dinosaurs and pterosaurs which were it seems homeotherms)
which lay shelled eggs (except for some snakes and Mesozoic marine reptiles that give or gave birth to live young), with a skin covered in scales and/or scutes (or secondarily smooth
as with some of the afore-mentioned marine reptiles). If this sounds excessively vague, you can understand why many have made the switch to cladistics. On the other hand, it still
serves, like "protist, "plant", "invertebrate", or "fish", as a useful generic term that is a lot easier to say and use then "any amniote that is not a bird or mammal". The same ease of use
applies to other paraphyletic terms, which is why we have retained them, rather than resort to tedious phrases such as, to give just one example, "non-crocodylomorph, non-dinosaur,
non-pterosaur stem-group archosaur/archosauriform" when the old 19th century term "thecodont" would in that instance serve quite nicely.
As for the cladistic (as opposed to Linnaean) definition of Reptilia, which is the most recent common ancestor of all recent reptiles and all their descendents (see technical definition
below.), this term is now redundant, since it depended on a particular group of prehistoric reptiles, called mesosaurs, diverging from the phylogenetic tree imemdiately after synapsids
but before all other groups. Since this is now pretty much agreed not to be the case, clade Reptilia becomes synonymous with clade Sauropsida, assuming teh traditional hypothesis of
turtles (testudines, chelonia) as anapsida holds. However, if turtles and their ancestors turn out to be diapsids (and more specifically crown group diapsids), that means only diverged
much later. In thios case, Reptilia becomes a sub-clade of Sauropsida. All of which shows what a world of controversy something as unassuming as phylogeny can be. MAK111121,
Image credits: Dragon, Dani 7C3, Wikipedia; Cladogram Petter B�ckman, Wikipedia, Evolution of reptiles from Schaffer/Bonine/Ferriere
Notes
[1] There was a time when one of us (MAK) was quite impressed with neuroscientist Paul MacLean's model, which was a standard part of the "New Paradigm" worldview of the late
70s and 80s and popularised by Carl Sagan (Dragon's of Eden), and also referred to by other authors such as Arthur Koestler and Erich Jantsch. But, as is so often the case, science
moves on. See for example Bruce & Neary 1995, Lanuza et al 1998 (references via Neuro-Dojo), Striedter 2005, and Patton 2008 (refrences via Wikipedia)
Descriptions
Reptilia: LCA Turtles and birds (link).
Range: from the Late Carboniferous.
Phylogeny: evolutionary systematic definition: see stem amniota
cladistic definition (1): Originally defined as Sauropsida: Mesosauridae + *: Anapsida + Eureptilia. Definition no longer
holds, now that mesosaurs are almost universally considered anapsids,
cladistic definition (2): LCA of all living reptiles. If turtles are anapsids, Reptilia is synonymous with Sauropsida. If they are
diapsids, Reptilia is synonymous with Sauria. MAK111121
Characters: Tabular small or absent; large posttemporal fenestra; suborbital foramen (small hole near the lateral edge of
palate, between the pterygoid, palatine, and ectopterygoid or jugal, when ectopterygoid absent); supraoccipital plate narrow.
Links: Class Reptilia; THE EMBL REPTILE DATABASE; Reptilia - Suite101.com; Introduction to the Diapsids; Reptilia
(Reptiles); Nuova pagina 1; BIOSIS | Resource Guide | Reptilia; Class Reptilia; Reptiles; Phylogeny and Classification of
Amniotes; Photogallery: Reptilia \ Amphibia. ATW020623.
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Amniota : Sauropsida
Contents
Abbreviated Dendrogram
REPTILIOMORPHA
|
`--AMNIOTA
|--Casineria
|--Westlothiana
`--Crown Amniota
|--Sauropsida (= Reptilia)
| |--ANAPSIDA
| `--EUREPTILIA
`--SYNAPSIDA
Overview
Stem Amniota
Crown Amniota
Reptiles
Sauropsida
Dendrogram
References
Taxa on This Page
1. Sauropsida
The Sauropsids
Sauropsida includes most of what was clasically known as "Reptilia" along with birds (which are in effect glorified
reptiles) and of course dinosaurs. Sauropsids therefore are the bulk of the reptiles plus birds, while Synapsids are the
"mammal-like reptiles" plus mammals.
The first Sauropsids were probably primitive lizard-like creatures
rather similar (and fairly closely related) to the protorothyrid
Hylonomus, shown at right.
They scurried through the
Carboniferous undergrowth. In appearance and behaviour they
would have been similar to modern lizards, although
anatomically they were more primitive. At this time, the world
was ruled by stem tetrapods. The only other amniotes around
were a few basal synapsids. Both groups underwent a rapid
evolutionary radiation as the Carboniferous and Permian
proceeded. The synapsid "pelycosaurs" grew into 1 to 3 metre
long predators, including specialized fin-back forms and two
herbivorous lineages. The sauropsids remained small and lizard-like. Thus the dominant life-form during the Permian
were synapsids, and, during the Late Permian, the therapsids which evolved from them. The end-Permian extinction,
which saw off 95% of lifeforms on Earth, decimated both synapsids and sauropsids, but the sauropsids came back faster,
with creatures such as the crocodile-like Proterosuchidae. These sprawling predators were the advance guard of a great
army of scaly and armoured carnivores and herbivores (the Archosauriformes ), as well as the dinosaurs, during the
Triassic period. Meanwhile the Triassic seas were the home of a variety of Sauropsid marine reptiles - ichthyosaurs,
nothosaurs, and thalattosaurs.
During the Late Triassic period the dinosaurs well and truly took over. The Synapsids were reduced to the role of
mouse-sized rodents and insectivores; the mammaliforms and mammals of the Late Mesozoic. They remained in that
lowly station, sharing the microvertebrate niches with a variety of lepidosaurs (lizards and lizard relatives), until a
huge asteroid saw off the dinosaurs and the marine reptiles (the terminal Cretaceous extinction event) and the
mammals were able to inherit the Earth. The surviving sauropsids include turtles, lizards, crocodiles and birds, all of
which are still around today. The crocodile-like Choristodera were a major group (order) of reptiles that survive the
terminal Cretaceous extinction but became extinct before the modern era, while the sphenodonts, the "lizards of the
mesozoic" one could call them, are represented by a single endangered species on a few small islands off New
Zealand.
Descriptions
Sauropsida: All amniotes closer to snakes than to St. Patrick.
Range: from the Late Carboniferous.
Phylogeny: Amniota : Synapsida + * : Reptilia + Eureptilia
Characters: Little or no specialization along tooth row; $ maxilla separate from quadratojugal; $ single coronoid;
some suborbital fenestra present; $ supinator process parallel to humeral shaft; $ 1 centrale in ankle; tail- based
locomotion using lateral undulation; frequently bipedal; no glandular skin, uric acid waste, beta keratin. ATW010219.
Comment: With Mesosauridae now included in the Anapsida, Sauropsida and Reptilia become synonymous. If turtles
are diapsids then Reptilia become synonymous with whatever "eosuchian" clade includes the most recent common
ancestor of all extant Sauropsids. MAK111105,
Links: Phylogeny and Classification of Amniotes; Taxonomy browser (Sauropsida); Lecture 8 - Tetrapods; Amniota.
ATW010219.
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Amniota: Dendrogram
Contents
Abbreviated Dendrogram
REPTILIOMORPHA
|
`--AMNIOTA
|--Casineria
|--Westlothiana
`--Crown Amniota
|--Sauropsida (= Reptilia)
| |--ANAPSIDA
| `--EUREPTILIA
`--SYNAPSIDA
Overview
Stem Amniota
Crown Amniota
Reptiles
Sauropsida
Dendrogram
References
This is surely one of the smaller dendrogram pages on Palaeos, as not much is known regarding stem amniotes. We
have tentatively placed Casineria and Westlothiana here, as they fit the expected pattern of miniaturisation combined
with advanced amniote features, but they could just as easily as easily go among the Reptiliomorpha. Most cladistic
analyses actually place those two taxa beneath the diadectomorphs (almost certainly amphibians) and
Solenodonsaurus, leaving the amniote ancestor unknown; the present author considers this could also be an artifact of
diadectmorph convergence with early reptiles; as with multiple mammal-like lines of therapsids and bird-like lines of
coelurosaurs there were clearly a number of lineages indepedently evolving in the same direction. MAK120321
REPTILIOMORPHA
|
`--AMNIOTA
|--Casineria •X
|--Westlothiana •X
`--Crown Amniota MH, ToL
|--+--Sauropsida MH / Reptilia | |--ANAPSIDA | `--EUREPTILIA `--SYNAPSIDA
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Amniota: References
Contents
Abbreviated Dendrogram
REPTILIOMORPHA
|
`--AMNIOTA
|--Casineria
|--Westlothiana
`--Crown Amniota
|--Sauropsida (= Reptilia)
| |--ANAPSIDA
| `--EUREPTILIA
`--SYNAPSIDA
Overview
Stem Amniota
Crown Amniota
Reptiles
Sauropsida
Dendrogram
References
Benton, M.J. 2005. Vertebrate palaeontology. 3rd ed. Blackwell publishing, Oxford.
Temporal Fenestration and the Classification of Amniotes
Bruce LL, Neary TJ. 1995. The limbic system of tetrapods: A comparative analysis of cortical and amygdalar
populations. Brain, Behavior and Evolution 46(4-5): 224-234.
Reptiles - note
Carroll, R. L. 1970. Quantitative aspects of the amphibian-reptilian transition. Form. Funct. 3:165–178.
Casineria
Carroll, RL (1988), Vertebrate Paleontology and Evolution, W. H. Freeman and company, New York
Carroll, R. L. 1991. The origin of reptiles. Pages 331–353 in Origins of the higher groups of tetrapods—controversy
and consensus (H.-P. Schultze, and L. Trueb, eds.). Cornell University Press, Ithaca.
Casineria
Lanuza E, Belekhova M, Martinez-Marcos A, Font C, Martinez-Garcia F. 1998. Identification of the reptilian
basolateral amygdala: an anatomical investigation of the afferents to the posterior dorsal ventricular ridge of the lizard
Podarcis hispanica. European Journal of Neuroscience 10(11): 3517-3534.
Reptiles - note
Laurin, M. 2004, The Evolution of Body Size, Cope's Rule and the Origin of Amniotes Syst. Biol. 53(4):594–622,
2004 DOI: 10.1080/10635150490445706
Casineria
Müller, J & RR Reisz (2005), An early captorhinid reptile (Amniota: Eureptilia) from the Upper Carboniferous of
Hamilton, Kansas. J. Vert. Paleontol. 23: 561-568.
Amniota
Patton, Paul (2008). "One World, Many Minds: Intelligence in the Animal Kingdom". Scientific American. December,
2008
Reptiles - note
Paton RL Smithson TR and Clack JA 1999. An amniote-like skeleton from the Early Carboniferous of Scotland.
Nature 398: 508-513.
Casineria
M. Ruta, M. I. Coates, and D. L. J. Quicke. 2003a. Early tetrapod relationships revisited. Biological Reviews
78(2):251-345
Ruta, M., Jeffery, J. E. and Coates, M. I. 2003b. A supertree of early tetrapods. Proceedings of the Royal Society of
London Series B-Biological Sciences 270: 2507-2516. . pdf
Casineria
Smithson, T.R. & Rolfe, W.D.I. (1990): Westlothiana gen. nov. :naming the earliest known reptile. Scottish Journal of
Geology no 26, pp 137-138.
Westlothiana
Striedter, G. F. (2005) Principles of Brain Evolution. Sinauer Associates.
Reptiles - note
van Tuinen M, and Hadly EA (2004) Error in estimation of rate and time inferred from the early amniote fossil record and
avian molecular clocks. J. Molecular Evolution 59(2): 267-276. pdf
Westlothiana
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